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B.A., Central College, 1983 


submitted in partial fulfillment of the 

requirements for the degree 


Department of Chemistry 


Manhattan, Kansas 


Approved by: 









1. Introduction and Ancient History 1 

2. First Scientific Investigations 7 

3. Aqueous Metal Sols 11 

4. Protective Colloids 18 

5. Non-Aqueous Metal Sols 21 


1. Preparation of Metal Sols 25 

2. Concentration Studies - Gold/Acetone 26 

3. Concentration Studies - Silver/Acetone .... 39 

4. Concentration Studies - Copper/Acetone .... 50 

5. Warmup Studies - Gold/Acetone 51 

6. Spectroscopic Studies - Gold/Acetone Sols 

A. UV - Visible 65 

B. NMR 66 

7. Electrophoresis - Gold/Acetone Sols 69 

8. Miscellaneous Observations - Metal Sols ... 79 

9. Film Formation - Gold/Acetone Films 82 

10. Pyrolysis/M.S . - Gold/Acetone Films 84 

11. Pyrolysis/G.C. - M.S. - Gold/Acetone Films. 91 

12. Infrared Studies - Gold/Acetone Films 94 

13. General Conclusions 98 



1 . Equipment and Parameters 100 

2. Summary of Reactions 104 






1. Gold/Acetone Colloid 30 

2. Particle Size Distribution 31 

3. Gold/Acetone Colloid 32 

4. Particle Size Distribution 33 

5. Gold/Acetone Colloid 34 

6. Particle Size Distribution 35 

7. Gold/Acetone Colloid 36 

8. Particle Size Distribution 37 

9. Concentration vs. Particle Size, 

Au/Acetone Colloids 38 

10. Silver/Acetone Colloid 40 

11. Particle Size Distribution 41 

12. Silver/Acetone Colloid 42 

13. Particle Size Distribution 43 

14. Silver/Acetone Colloid 44 

15. Particle Size Distribution 45 

16. Concentration vs. Particle Size, 

Ag/Acetone Colloids 46 

17. Gold/Acetone Colloid 53 

18. Particle Size Distribution 54 

19. Gold/Acetone Colloid 55 

20. Particle Size Distribution 56 

21. Gold/Acetone Colloid 57 

22. Particle Size Distribution 58 

23. Gold/Acetone Colloid 59 


FIGURES (continued) 


24. Particle Size Distribution 60 

25. Gold/Acetone Colloid 61 

26. Particle Size Distribution 62 

27. Gold/Acetone Colloid 63 

28. Particle Size Distribution 64 

29. Proton NMR Spectrum 67 

30. Proton NMR Spectrum 68 

31. Diagram of Electrophoresis Cell 71 

32. Mass Spectrum, Pyrolyzed Gold Film 87 

33. Mass Spectrum, Pyrolyzed Gold Film 88 

34. Mass Spectrum, Pyrolyzed Gold Film 89 

35. Mass Spectrum, Pyrolyzed Gold Film 90 

36. IR Spectrum 96 

37. IR Spectrum 97 

38. Vacuum System and Metal Atom Reactor 101 




1. Types of Colloids 2 

2. Raw Data from Electrophoresis Experiment 72 

3. Zeta Potentials, Gold/Acetone Colloids 75 

4. Zeta Potentials, Other Authors (aqueous) 76 

5. Average Charge on Colloidal Particles 77 

6. Conductances of Various Gold/Acetone Colloids .... 79 

7. Elemental Analyses of Gold/ and 

Silver/Acetone Colloids 82 

8. Summary of Pyrolysis/G.C. /M. S. Experiments 92 

9. Summary of Reactions 104 


The author wishes to thank the following people for their 
assistance and helpful discussions: Thomas Groshens, Michael 
Brezinski, Alan Olsen, David Devore, Dr. S.T. Lin, Dr. Galo 
Cardenas Trivino, and Dr. Ejnar Moltzen. 

Special thanks to Dr. Kenneth J. Klabunde for financial 
support, guidance and patience. 


for Melinda 


1.1. Introduction and Ancient History 

The term "colloid' was coined by T. Graham to describe 
suspensions of small particles in a liquid (1). His investi- 
gations on suspensions of sulfur, prussian blue and casein with 
respect to their diffusion rates in water (which is slow) led him 
to differentiate between them and such substances as KOH, MgSO^ 
and sugar (which diffuse rapidly). He referred to the former as 
colloids and the latter as crystalloids. The different behaviors 
of these two classes of substances toward a semipermeable membrane 
(such as hog intestine) was also striking: crystalloids in 
solution would pass readily through the membrane, but colloids 
would not. This made it possible to separate the two. This 
process is called dialysis. 

"Colloid" eventually took on the more general meaning of any 
dispersed system, in general one in which the dimensions of the 
dispersed phase range from approximately 1 nm to approximately 
500 nm (10-5000 A). (2) 

Colloidal particles cannot be seen by ordinary optical 
microscopes, nor are they filterable by ordinary means. 

The following table summarizes the various types of colloidal 
systems, along with their common names: 

Table I (3) 

Dispersion medium Dispersed phase Common names 

Gas Liquid Fog, Mist, Aerosol 

Gas Solid Dust, Fume, Smoke, Aerosol 

Liquid Gas Foam 

Liquid Liquid Emulsion 

Liquid Solid Sol, Colloidal solution 

Solid Liquid Gel, Solid emulsion 

Solid Solid some Alloys, Glasses 

The main topic of this thesis is gold colloids or sols; with 
special emphasis on those in non-aqueous dispersion medium. It 
is well at this point to discuss the history of gold colloids. 

Man's fascination with gold is older than recorded history. 
Since gold is found almost exclusively in the elemental form in 
nature, and is soft, easily worked and does not tarnish, it was 
probably the first metal with which early humans became 
acquainted. Its fascination still holds, and even today gold is 
synonymous with wealth. This fascination led people to believe 
early on that gold also had magical and mysterious properties. 
In most early alchemical schemes, gold was the center of atten- 
tion. Efforts were directed towards synthesizing gold from 
cheaper materials, or towards freeing other "base" metals from 
the impurities which were believed to differentiate them from 
gold. Gold was the "perfect" metal, and other metals and 
materials could theoretically be "perfected', at which point they 
would become gold. It was only natural at this point to ascribe 
great medicinal powers to gold, and, not incidentally, to the 
reagent capable of transmuting base metals into gold. As Roger 
Bacon (12147-1294) said: "For the medicine which could remove all 


impurities and corruptions from base metal so that it could 
become the purest silver or gold is considered by the wise to be 
able to remove the corruptions of the human body to such a degree 
that it could prolong life through many ages." (4) 

The first recorded efforts in this area were by the ancient 
Chinese. In about 142 A.D. a work appeared called Ts 'an t ' ung 
ch ' i by one Wei Po-yang. In it, he gives the primary aim of 
Chinese alchemy: "Longevity is of primary importance in the 
grand triumph.... The men of the art, feeding on [gold], attain 
longevity." (5) 

There are references in the Pao-pu-tzu of Ko Hung (2817-361? 
A.D.) to the consumption of Chin i_ (gold fluid) to prolong life. 
(6) It is doubtful that this was a colloidal solution (or even 
if it actually contained gold), since aqua regia was unknown to 
the early Chinese alchemists. They did, however, make use of Hg 
amalgams, and it is possible that they were able to form some 
sort of dispersion using this. 

The discovery of true colloidal gold had to wait until the 
discovery of aqua regia, which is the only solvent which can be 
employed to dissolve gold under ordinary conditions. The first 
record of aqua regia appears in Summa Perf ectionnis Magisterii , 
commonly ascribed to Geber. (7) Geber is the Latin form of the 
name of Jabir ibn Hayyan, the most celebrated of Arabic 
alchemists, who is supposed to have been active in the ninth 
century. In all probability, Summa Perf ectionnis Magisterii was 
written by a practicing Spanish alchemist in about 1310. It was 

frequently quoted and copied by others. (8) 

In medieval Europe, as in ancient China, there was an 
interest in the medicinal properties of gold. Various recipes 
for aurum potabile (drinkable gold) appeared in the literature 
of the time. In many cases these contained no gold at all, as in 
the recipe of Arnold de Villanova (1235-1311), which called for 
quenching a hot gold plate in a bucket of wine. (9) In general, 
though, aurum potabile consisted of what we call today colloidal 
gold. A solution of gold in aqua regia (in which it exits as 
AUCI3 or HAUCI4) was reduced by treatment with ether or ethereal 
oils (10). It was usually then treated with chalk to neutralize 
it and make it fit for consumption. Fabulous curative powers 
were attributed to these solutions, especially towards heart 
disease. In many astrological schemes, the sun controlled the 
heart and the sun was also mystically associated with gold. (11) 

In 1618 Franciscio Antonii published " Panacea Aurea: Auro 
Potabile " (12) which was about colloidal gold. Antonii was a 
physician and his book centered on the use of aurum potabile in 
the treatment of venereal diseases, dysentery, epilepsy, tumors, 
etc. He claimed to have successfully treated many patients (13). 
In 1676, Johann Kunckels published a book entitled, " Niitzliche 
Observationes oder Anmerkungen von Auro und Argento Potabile " 
(14). In this treatise Kunckels noted that preparations usually 
called "drinkable gold" actually contained metallic gold in a 
clear, slightly pink solution. Thus he concluded that the gold 
must be in pieces so small that the eye could not detect them. 

He also attributed curative power to these preparations. 

In 1718 a treatise on colloidal gold appeared entitled, 
" Aurum Potabile oder Gold Tinctur " by Hans H. Helcher, a doctor 
of medicine (15). In it he described primarily the medicinal use 
of colloidal gold, but most important to modern readers, he 
pointed out that the addition of boiled starch would noticeably 
increase the stability of the preparation. This was confirmed by 
later workers who investigated the action of so-called protective 
colloids, polymeric, lyophilic materials which when adsorbed onto 
the surface of colloids, tended to stabilize them. 

Gold colloids were mentioned by J. Juncker in 1730 (16), and 
also by P.J. Macquer in 1789 (17). In 1802 Richter published 
" Ueber die neuren Gegenstande der Chymie " (18), in which he 
mentioned that the colors of purple gold solutions and ruby glass 
were due to the presence of finely divided gold (19). He 
correlated the color of gold solution with particle size, saying 
that the pink or purple solutions contained the finest particles, 
and that the gold color appeared only after the particles had 
grown to a certain size (20). A Mrs. Fulhame published in 1794 
an account of how she had used a colloidal gold solution to dye 
silk cloth, resulting in various shades of purple (21). 

A parallel development to that of colloidal gold was the 
development of the so-called Purple of Cassius. Addition of a 
solution of stannous chloride to one of auric chloride results 
in the precipitation of stannic hydroxide and the reduction of 
gold to tiny particles which precipitate in various shades of 

brown, purple, blue or red. This reaction is also used as the 
basis for a very sensitive qualitative test for gold. The sample 
is dissolved in aqua regia and boiled, then added to a saturated 
solution of stannous chloride. It has been shown that 10 p.p.b. 
can be detected by this method (23). 

J.R. Glauber mentioned the precipitation of a purple material 
by tin from a gold/aqua regia solution (24). In 1684, A. Cassius 
described completely for the first time this reaction (25). The 
materials prepared in this way found extensive use as agents for 
coloring red glass. Often this color does not appear when the 
gold reagent is added to the glass, but annealing the glass just 
below its melting point brings out a brilliant ruby red color 

1.2. First Scientific Investigations 

The first thorough scientific investigation of gold sols was 
carried out by Michael Faraday and published in 1857 (22). The 
principal object of Faraday's study was the properties of light. 
To this end he studied gold and silver leaf, and various films of 
these metals. In conjunction with this he studied gold sols made 
by several methods, all of which were reductions of AUCI3 in 
aqueous solution with various reducing agents: phosphorus in 
ether, phosphorus in carbon disulfide, phosphorus alone, etc. He 
also studied aerosols produced by sparking a gold wire with the 
discharge from a Leyden condenser. He concluded from his investi- 
gations that the gold is actually present in the elemental form, 
and that the color of the colloidal solution is a function of the 
particle size. He added NaCl solutions to the gold sols and 
observed that the color changed from red to purple, and was 
accompanied by f locculation. He also studied the filtration of 
these sols and found that they could pass through filter paper 
unchanged. He also discovered the phenomenon of light scattering 
by colloids: when a beam of light was passed through a dilute 
gold sol, the beam was visible as a cone of light where it passed 
through the sol. This phenomenon is called the Tyndall cone 
effect . 

All of the gold sols known up to this point had two things 
in common: they were formed by the reduction of AUCI3 and they 

were in aqueous solution. This has continued to be the favored 
method for the production of gold sols, but some other methods 
have been used as well. 

In 1898, Bredig described a method for the formation of 
metal hydrosols by the use of an electric arc (27). Two 
electrodes made of the metal of interest, are brought close 
together under water. High voltage (40-50 V, 5-10 A) was applied 
across the electrodes, and the arc formed generated colloidal 
metals from the electrodes. Colloids of lead, tin, gold, 
platinum, bisimuth, antimony, arsenic, thallium, silver and 
mercury have been prepared by this method (28,29,30). It has 
been found by these workers that some sols are more stable when 
formed in dilute acid or base solutions. Mindel and King 
investigated Pt sols formed by the Bredig method and determined 
that the particles were stabilized by platinic oxide and hexa- 
hydroxyplatinic acid, which were formed from hydrolysis of water 
and not from atmospheric oxygen (31). Bredig also attempted to 
form organosols by his method, but these efforts were unsuccessful 
due to the decomposition of the solvents under experimental 
conditions. Svedberg modified Bredig's apparatus somewhat, by 
striking the electric arc in a glass tube under the surface of the 
liquid. A small hole was placed in the side of the tube near the 
arc ends of the electrodes. Gas was passed through the tube and 
out the small hole, bubbling up through the liquid and carrying 
with it the small metal particles generated by the arc. Svedberg 
was able to use this method to prepare some stable metal 


organosols, using liquid methane, ether and isobutanol at low 
temperatures. Svedberg also used a slightly different method, in 
which electrodes such as those of Bredig are used in conjunction 
with a large induction coil and a large condenser. Fragments of 
the metal of interest are placed in the bottom of the vessel 
holding the solvent, and the arc from the discharge soon forms a 
sol (32,33,34). This method was also used for the production of 
organosols. Mayer obtained a patent on the use of a high voltage 
(100-200 kV) discharge to evaporate metal wires in liquid media. 
The liquid used was 48% betaine or 48% benzidine in water. Using 
gases instead of liquids as the dispersion medium yields aerosols 
(75). Bredig and Haber used a high voltage discharge to disinte- 
grate cathodes of Pb, Sn, Bi , Sb, As, Th, and Hg in a aqueous 
NaOH solution (77). Kimura used a modified form of Kohlschutter ' s 
apparatus (arcing metal electrodes in an air stream) to form 
aerosols of Pt , An, Ag, Al , Ni, Fe, Cn. When these aerosols were 
swept into water by a has stream, hydrosols were formed (78,79). 
Karioris, Fish and Royster made metal aerosols by exploding metal 
wires in air and other gases with high voltage (1-18 kV) (80). 

In 1935, Pauli, Russer and Brummer made stable gold sols by 
electrically sputtering gold metal into an aqueous HC1 solution. 
Pauli and Schild also used this method for the production of a Pt 
sol (81,82). 

Matsumura reported the formation of colloidal silver in the 
following way: a mixture of AgN03 solution and MgO was pulverized 
and kneaded into a paste. Dilute acetic acid was added to 

dissolve MgO, and the resulting colloidal solution of Ag was 
filtered and then electrodialyzed to remove excess ions (83). 

Kimoto, Kamiya, Nonoyama and Uyeda noted that aerosols could 
be produced by evaporation of various metals (Mg, Al, Cr , Mn, Fe, 
Co, Ni, Cu, Zn, Ag, Cd , Sn , Au , Pb, and Bi) from a hot tungsten 
wire into a chamber containing He or Ar from 1-30 tons pressure 
They found that at low pressures, smaller particles were formed, 
and at higher pressures, larger particles. N. Wada used this 
method with Ar gas and confirmed the earlier findings (84,85). 

In 1983, K. Kimura and S. Bandow reported on the formation 
of metal colloids both by codeposition of gold vapor and ethanol 
vapor in a cold matrix and by the evaporation of metal into a gas 
stream which is then bubbled through a cold solvent (usually 
ethanol) (35). This work was unknown to this author until 1985. 
Efforts to replicate Kiraura's and Bandow's work in our laboratory 
have thus far met with limited success. 


1.3. Aqueous Metal Sols 

This has been the most common route to metal colloids in 
aqueous dispersion media. Typically the metal halide (occasional- 
ly the oxide) is the starting material, and a variety of 
substances have been used as reducing agents. 

Faraday's methods of reducing gold chloride have already 
been mentioned. 

Gutbier reported in 1908 that a 0.1% sols of AUCI3 neutra- 
lized with Na2C03 could be reduced to colloidal gold when treated 
with hydrazine hydrate, hydroxylamine hydrochloride or phenyl- 
hydrazine hydrochloride. In his study, dilute sols resulted in a 
red color, while more concentrated sols were blue (36,41). 

Thomae reduced AUCI3 solutions with K2CO3 and formaldehyde, 
and also replicated Faraday's work with an ethereal solution of 
phosphorus (37). 

Hydrogen peroxide was used as a reducing agent for aqueous 
HAuCl^ by Doerinckel. He found that addition of a small amount 
of preformed gold colloid would facilitate the formation of a 
uniform sol. He also found that the particle concentration was 
proportional to the amount of "seed" colloid used (38). 

Zsigmondy also studied this "seeding" phenomenon. He added 
AUCI3 solution to a gold sol in the presence of a reducing agent 
and found that the reduced gold was deposited on the particles 
already present, increasing their size. This would later lead to 


important conclusions about the mechanisms of particle nucleation 
and growth. Zsigmondy studied this experiment with the aid of 
the slit ultramicroscope, about which more will be said later 
(39). Reitstotter also studied the seeding phenomenon (47) as 
did Zakowski. Zakowski found that particle growth occurred in 2 
stages: slow growth, in which the size of the particles does not 
increase very fast, and a fast growth period. The first stage 
can be thought of as an induction period. Zakowski found that 
increasing the surface area of the "seeds" or increasing the 
temperature or exposure to U.V. light shortens the induction 
period (53). 

Svedberg studied the reduction of metal salts and oxides in 
solution by a stream of gas bubbles. He found that AgO was 
reduced by H2 at 50 degrees C. He also reported reduction of 
AUCI3 in solution by CO, SO2 and formaldehyde (40). 

In 1914 Gutbier and Weingartner reported that AUCI3 could be 
reduced by an aqueous starch suspension under basic conditions. 
It was found that the starch macromolecules were adsorbed on the 
surface and helped to stabilize the colloid. Moving-boundary 
electrophoretic measurements indicated that the starch-coated 
colloid behaved approximately like a neat starch solution (42). 

Colloidal gold and silver were obtained by Granert by 
heating a basic solution of the protalbin or lysalbin acid salt 
of silver or gold, and dialyzing the resulting sol to remove 
excess ions. Again, it was found that the long macromolecules 
adsorbing on the surface of the particles tended to stabilize 


them. Granert exploited this fact by stabilizing Au, Pt, Pd , Ir 
and Ag colloids with serum albumin. He used hydrazine hydrate to 
reduce the salts of these metals in a solution containing the 
serum albumin (A3). 

An interesting method for the reduction of gold salts was 
reported by Donau in 1915. He made a blue gold hydrosol by 
playing the reducing portion of a hydrogen flame across the 
surface of an auric chloride solution (44). Halle and Pribram 
proposed that the reducing species in this instance was HNO3 
formed in the water by the oxidation of atmospheric N2 by the 
heat of the flame (45). Donau also used a spark discharge just 
under the surface of a AUCI3 solution, and found that this forms 
a red hydrosol (44). 

Groll reported that in the reduction of AUCI3 by H2O2 in 
aqueous solution the pH of the solution had an effect on the 
color of the colloid formed. At low pH, the sol would be red, 
while in more basic solutions, the color would be blue (46). 

During the early years of the 20th century, research in gold 
colloids was stimulated by the discovery that the cerebrospinal 
fluid of a person infected with syphillis would precipitate 
certain gold colloids, while that of a healthy individual would 
not. This was used as the basis for a diagnostic routine known 
as the Lange colloidal gold test. One problem with the test was 
the near-impossibility of repeatably making identical gold 
colloids. Much work was done in an effort to standardize the 
preparation of colloidal gold used for this purpose. Black 


published a reductive method which he found to be reproducible 
(48). Speidel and Smith reviewed various preparations of colloid- 
al Au for this purpose, and found that it was very important that 
both the water and glassware used be completely free from any 
contaminants (49). Manheim and Bernhard described the use of an 
electric arc for the preparation of the colloid, and found that 
it was also useful for the Lange test (50). Nicol reported that 
equimolar amounts of urea and H2O2 would reduce gold chloride to 
form a red colloid suitable for the Lange test (51). 

Domanitzkii found that almost any unsaturated hydrocarbon 
could be used to reduce HAUCI4 in aqueous solution. He used 
acetylene, allene and 2-methyl-2-butane, and found that they also 
worked for the reduction of AgCl to a silver colloid (54). 

One of the more bizarre reducing agents used has been wine, 
as reported by Iwase in 1930. He found also that Japanese sake 
did not work as well as wine (55). Other plant materials have 
also been used as reducing agents: Iwase used aqueous plant leaf 
extracts for this purpose, and N. von Veimarn used extracts from 
pea petals, cloves, azaleas, peonies, roses and chrysanthemums to 
form a red gold sol (56,57). Rimini reported that adding AUCI3 
solution dropwise to a fresh aqueous yeast suspension, followed 
by extensive filtration and treatment with NaOH, more filtration 
and neutralization with HCI resulted in a bluish gold colloid, 
but one that was only stable for approximately one week (58). 
Liversidge also published an account of AuCl , reduction by a 
yeast, aspergillus oryzae , to form a gold sol (59). 


A silent electric discharge was used by Miyamoto to reduce 
an HAuCl^ solution (60). A similar method was used by Pavlov to 
make colloidal gold, copper, silver, and lead from AUCI3, Cu + 2 
salts, AgN03 and Pb (0Ac)2 solution, respectively. A four to 
five cm. layer of distilled water was carefully added on top of 
an electrolyte solution in a partially filled U-tube. A Pt 
cathode was suspended above the water layer, and a Pt anode was 
immersed in the electrolyte in the other limb of the U-tube. A 
potential sufficient to form an arc between the cathode and the 
water layer was then applied. This was supposed to form C>2~ 
anions which then diffused through the water and reacted with the 
cations which have migrated to the cathode. The reduction by 02" 
was unaffected by other anions present (61). 

Galecki reported that silver sols could be prepared from AgO 
or AgNC>3 using Na2C03, K2Q, CO3 , KOH, NH3, ethereal solutions of 
P, aqueous H2SO4, or hydrazine hydrate. He also investigated the 
light sensitivity of the Ag sols formed (62). 

Sodium citrate was used to reduce AUCI3 in aqueous solution 
by Scherre in 1950. He found that the stability of the resulting 
red sol could be improved by the addition of ascorbic acid 
(vitamin C) , which was presumably adsorbed on the surface of the 
gold particles (63). 

Suito and Ueda discovered an interesting correlation between 
the absorbtion spectra of gold sols formed by reduction with a 
formalin solution and the particle size as determined by electron 
microscopy (64). 


The growth of colloidal gold particles in a gold trichloride/ 
hydroxylamine/dilute HC1 solution was studied by Turkevich, 
Stevenson and Hillier. They found that the particle size distri- 
bution curve was determined by two separate kinetic processes: 
nucleation and growth. Using the assumption that the spread of 
the particle size distribution is directly proportional to the 
spread in time of nuclei formation, they were able to analyze the 
particle size distribution curves and obtain data about the rates 
of particle growth and nucleation (65,66). This group made 
extensive use of the electron microscope. 

Suito and Ueda also used the electron microscope to study 
the crystalline morphology of colloidal gold reduced with 
salicylic acid at room temperature. Their investigation showed 
that most particles had a threefold symmetry azis and were flat. 
They noted Moire fringes and surmised that these were due to the 
presence of step defects which were slightly offset one from 
another as the step grew angularly about the center of the 
crystal. Interestingly, it was noted that some of the flat 
crystals had holes in the center. Based on the threefold 
symmetry, they concluded that growth occurred on the (111) plane 

Chiang and Turkevich confirmed the work of Suito and Ueda 
and also observed holes in the center of platelike particles with 
approximately 1000 A diameters (the particles). Chiang and 
Turkevich also noted that the platelike form is not the first one 
produced, but is the result of aggregation and rearrangement of 


the smaller particles that were initially formed. They also 
produced some platelike particles of platinum and palladium (68). 

Fabrikanos, Athanassiou and Leiser reported the preparation 
of stable gold and silver hydrosols by reduction with disodium 
ethylenediaminetetraacetate (69) . 

In 1969, Machalov, Groisberg, and Palikov reported the 
formation of colloidal Au, Ag, Pd , Os, Rh, Pt , Sn, Te and Tl from 
their nitrates using KBH4 as a reducing agent in an aqueous 
solution of pH 9 containing 5% gelatin at 40 C. The products 
initially formed in the reaction were unstable and decomposed to 
form the colloids. It was found that the addition of a small 
amount of poly ( vinylalcohol) increased the stability of the 
colloids (70). 

Brede, Mehnert, Franke, Roschke and Herrmann obtained a 
patent on a process for the production of gold colloids by light. 
An aqueous mixture containing a metal salt, an aromatic or 
aliphatic substituted ketone as a light acceptor, an alcohol as a 
proton donor, and a detergent to stabilize the colloid formed, 
was irradiated for 60 minutes with light from a Xe lamp ( 3. = 350 
nra). With an aqueous solution of HAUCI4, isopropanol and 
benzophenone they formed a gold sol with particle size of 
approximately 100 nm which absorbed light of "X = 560 nm. Using 
sunlight, and irradiating for 180 minutes resulted in the forma- 
tion of a gold colloid with a particle size of approximately 50 
nm which absorbed at A = 540 nm (107). 


1.4. Protective Colloids 

Protective colloid is a term used to describe macromolecular 
or polymeric substances which stabilize other colloids (usually 
inorganic) by adsorption on the surface. This effect has been 
known for a long time. Faraday noted that gold sols are more 
stable in gummy gelatinous liquids (22). Lottermoser noted that 
albumin prevented the coagulation of silver sols by electrolytes 
(71). Gutbier, Huber and Kuhn reported in 1916 that the reduction 
of AUCI3 in a very dilute solution of icelandic moss with hydrzine 
hydrate gave a very stable gold sol. They noted that the sol 
thus formed could be precipitated by the addition of alcohol and 
then reversibly solvated by the distillative removal of the 
alcohol. This method also worked for making colloids of palladium 
from the reduction of PdCl2 (72). Granert found that gelatin and 
serum albumin made good protective colloids for silver and gold 
sols, respectively (43). Gutbier and Weingaertner used starch as 
a protective colloid for silver (42). Wegelin used gelatin as a 
protective colloid for the stabilization of several metal sols 
which he formed by grinding the metal with a soluble solid (76). 
Rimini used glucose to stabilize a gold sol formed by reduction 
of AUCI3 with a fresh yeast suspension (58). Gum arabic and 
gelatin were used to stabilize silver sols by Miyamoto (60). 
Scherre used ascorbic acid to stabilize a gold hydrosol (63). 
The use of polyvinyl alcohol as a protective colloid was reported 


by Machalov, Groisberg and Palikhov for the stabilization of Ag, 
Au, Pd, Os, Rh, Pt, Sn, Te, and Td sols (70). 

Natanson was able to make stable copper sols in acetone/ 
toluene/1-pentanol mixtures by agitation of Zn powder with CaCl2 
in the solution. No stable sols could be produced without the 
use of 0.001 - 0.01% natural latex or collodion as a protective 
colloid (73). Chu and Friel prepared colloidal cobalt in 
tetrahydrof uran dispersion medium by reduction of C0CI2 with 
sodium naphthalide. They postulated that the cobalt sol was 
stabilized by adsorbed naphthalene (74). Rampino and Nord 
stabilized colloidal palladium with polyvinyl alcohol and found 
that it was an efficient catalyst for the reduction of quinone 
and m-bromonitrobenzene to hydroquinone and m-bromoaniline in the 
presence of H2 (86). Uno, Ichiji and Kobayashi reported that 
the coagulation of frozen Au, Pt, and AS2S3 sols upon thawing was 
prevented by the presence of alcohols, sugars or urea. For 
alcohols, it was found that the protective action was increased 
with an increase in the number of -OH groups present (87). 

Jirgensons studied the protective action of various PVP 
(polyvinylpyrrolidone) fractions on silver sols and found that 
lower molecular weight fractions were more protective against 
coagulation by electrolyte addition than the higher fractions 
(88). Fujii and Sugiura compared the protective abilities of 
polyvinyl alcohol to those of gelatin and found that PVA did not 
protect inorganic colloids as well as gelatin against coagulation 
by electrolytes (89). Kubal used Na or K polyalkylacrylate both 


as reducing agents for AgN03 and as protective colloids for the 
resultant Ag colloids (90). Colloidal Pd protected with poly 
(N-vinyl - 2-pyrrolidinone) was used for selective catalytic 
hydrogenation of cyclopentachine in alcohol solutions by Hirai, 
Chawanya, and Toshima (91). 

The fact that long-chain molecules are adsorbed on small 
metal particles with concomitant stabilization of these particles 
has been exploited by biochemists as a labeling technique for 
biomolecules. Faulk and Taylor reported stabilizing Au sols with 
several types of antibodies which rendered the antibodies visible 
in the electron microscope (92). They also reported the use of 
colloidal Au as a label on rabbit anti-salmonellae serum 
(antibody), which retained full biological activity and allowed 
them to see the binding sites on the cell surface with the aid of 
an electron microscope. They also discussed the possibility of 
using two different particle sizes for a double labelling 
technique (93). 

Lee and Meisel performed surface-enhanced Raman spectroscopy 
experiments on Au and Ag colloids stabilized with poly (vinyl 
alcohol) (PVA), Carbowax 20 M, and poly ( vinylpyridine) (PVP). 
The bands observed by this experiment showed that PVA was absorbed 
through unhydrolyzed OAc groups, Carbowax by C-O-C groups and PVP 
by the pyridine Tf - system, giving flat ring coordination to the 
metal surface (108). 


1.5. Non-Aqueous Metal Sols 

Compared with the amount of work done on metal colloids in 
aqueous dispersion media, the amount of literature dealing with 
non-aqueous systems is quite small. 

Bredig attempted to make metal sols in organic liquids with 
his high voltage electric arc but found that the high potential 
needed to generate the arc tended to decompose the organic 
solvents (27). Svedberg was able to make sols of Fe, Cu, Ag, Al, 
Ca, Pt , Au, Zn, Sn, Cd , Sb, Tl , Bi and Pb in liquid methane, 
ether, isobutyl alcohol and other solvents at low temperatures. 
He modified Bredig's apparatus by the use of an alternating 
current and by placing small grains and pieces of the metal of 
interest in the bottom of the ceramic vessel used to hold the 
liquid. The discharge was then propagated among these small 
pieces and tiny particles of metal (colloidal) passed into the 
dispersion medium (94). Another method exploited by Svedberg 
used a gas flow to carry a metal aerosol formed by an electrical 
discharge between electrodes of the metal of interest into the 
organic solvent dispersion medium (34). Williams and Skogstrom 
reported in 1926 that a small amount of H2O would stabilize 
colloidal P2O5 in nitromethane dispersion medium (95). P.P. von 
Weimarn prepared colloidal Au by pouring a weak solution of AUCI3 
in glycerol into boiling glycerol and then rapidly cooling the 
solution after the appearance of a red color. Apparently the 


glycerol functions both as a reducing agent and as the dispersion 
medium (52). Natanson reported the production of colloidal Cu in 
an acetone/toluene/1-pentanol solvent by reduction of CuCl2 with 
Zn powder (73). Janek and Schmidt formed a gold/citrate hydrosol 
and added this to a solution of propanol with a small amount of 
toluene or nitrobenzene in a closed tube. The tube was then 
heated until one phase was formed, and then cooled. When two 
layers formed again, it was found that the Au colloid was in the 
alcohol-rich layer. This method also worked with t-butanol to 
yield a highly concentrated alcosol (96). Marinescu reported 
that sonication (treatment with ultrasound) of alkali metals and 
their alloys at their melting point in kerosene yielded pyrophoric 
colloids (97). Gibson and Baldwin noted that the subjection of 
200 V across a U-tube containing a two-phase system composed of 
H20/acetone/diethyl ether in the ratio of 12:19:10 would cause the 
migration of colloidal AS2S3, Au and bentonite (a clay mineral) 
from the H20-rich phase to the ether-rich phase (98). Gold 
organosols were prepared by Yamakita. He used 52 different 
dispersion media — fats, organic acids, alcohols, aldehydes, 
ketones, ethers, and various hydrocarbons and hydrocarbon deriva- 
tives (halogen, -NO2 and -NH2). The dispersion media were also 
the reducing agents for the starting material, AU2O3. He had the 
most success with fats and higher fatty acids which were weakly 
reducing. He reported particle sizes of approximately 300 A, 
determined by ultramicroscopy (99). In 1947, M.D. Marshall of 
Monsanto Chemical Co. obtained a patent on a process for forming 


Si02 sols in organic dispersion media. The first step was 
formation of the hydrosol. Then a miscible organic solvent 
(boiling point greater than 100 C) was added in an amount 
sufficient to precipitate the inorganic salts present. The salts 
were then removed by filtration, and the water removed by distil- 
lation. This method was successful for Si02 in butyl acetate, 
ethyl acetate, toluene and hydrocarbon oil fraction with boiling 
point 116 C (100). 

Khibvidze found that Pb sols in ethanol could be formed 
merely by shaking Pb powder in ethanol for an extended period. 
His studies revealed that an initially very fine dispersion would 
aggregate at first, but after prolonged agitation would again 
become fine. Initially coarse sols formed finer sols upon 
prolonged shaking (101). Van der Waarden studied the stabiliza- 
tion of carbon black in hydrocarbons by the addition of aromatic 
compounds with long aliphatic side chains. He postulated that 
these additives acted as a protective colloid for carbon black 

Colloidal cobalt in THF was reported by Chu and Friel. 
C0CI2 was reduced with sodium naphthalide to form colloidal Co 
(74). Broadbent, Campbell, Bartly and Johnson reduced RhOy with 
H2 gas in various solvents: p-dioxane, ethanol, glacial acetic 
acid and water. In acetic acid, they produced a black, air- 
sensitive rhodium colloid that was an efficient hydrogenation 
catalyst (103). Kukushova and Radulova produced colloidal Au in 
a number of turpentine oils, turpentines, lavender oil, rosemary 


oil, nitrobenzene and asphalt mixtures. The product was used to 
paint gold lines on ceramic products. Few details were given 
(104). Ledwith reported the formation of blue Au organosols in 
diazoethane mixtures with: diethyl ether, toluene, benzene, 
cyclohexane, chloroform, carbon tetrachloride and bromobenzene. 
The diazoethane reduced AUCI3 (1% solution in water) which was 
added dropwise to the organic solvent mixture (105). Blumencron 
reported that reduction of AUCI3 in olive oil fractions formed an 
organosol which could be injected with few harmful side effects 
for the treatment of arthritis (106). Colloidal Pd was produced 
in alcohol solutions by the reduction of PdCl2 poly (N-vinly-2- 
pyrrolidimone) , which also served as a protective colloid. 
Particle sizes of 18-56 A were reported (91). 

Some other non-aqueous systems have also been mentioned in 
the sections dealing with electrical discharge methods, protective 
colloids and miscellaneous methods, respectively. The interested 
reader should see the appropriate sections for the work of 
Natanson (73); Chu and Friel (7A); Hirai, Chawanya and Toshima 
(91); Svedberg (32,33,34); and Kimura and Bandow (35). 


II. 1. Preparation of Metal Sols 

In this study, the metal vapor technique was used for the 
production of colloidal metals in organic dispersion media. The 
equipment and general techniques of metal vapor chemistry have 
been covered extensively by other authors (109,110,111). 

The system comprised of gold and acetone was the one studied 
most extensively. Silver/acetone and copper/acetone were also 
found to form colloids by this method. Gold/ethanol and AgCl/ 
ethanol were attempted but did not result in stable colloidal 
solutions. Neither did Ag/DMF or Cu/DMF. 

Typically a small amount of metal (0.002 - 0.2 g) was 
vaporized and co-condensed with acetone vapor (41 - 199 mL). 
After an extensive period of trial and error, it was found that 
stable sols would only result if the matrix were warmed up 
slowly. Various liquid nitrogen/solvent slush baths were tried, 
as were various lengths of time with the slush baths. In general, 
it was found that merely pouring out the liquid nitrogen from the 
dewar surrounding the reactor and then replacing the cold, empty 
dewar would slow the warming sufficiently to form a stable sol, 
and this was adopted as the "standard" method. 


II. 2. Concentration Studies - Gold / Acetone 

It was necessary to investigate the influence that concen- 
tration had on the products (colloid) formed, particularly with 
regard to particle size and particle size distribution. The 
simplest and most direct way to gain information about the 
particle sizes of metal colloids is through electron microscopy. 
Indeed, gold colloids were one of the first subjects to occupy 
the attention of early workers in electron microscopy (115,116, 
117,118). Electron microscopy gives images of the particles 
under investigation, and therefore gives information not only 
about particle size and size distribution, but also particle 
morphology, degree of agglomeration and deformities. Electron 
microscopy has therefore been used to check the validity of other 
particle size determination methods: small angle x-ray scattering 
(119,120,123), absorption spectroscopy (121), ultracentrif ugation 
(122), and ultrasonically-induced optical birefringence (124). 
The morphology of colloidal Au particles was studied by Suito and 
Ueda. They found that under certain conditions, the particles 
would adopt a threefold symmetry, indicating growth on the 
crystallographic [111] plane (125,126). Colloidal gold was used 
in conjunction with electron microscopy to probe certain cellular 
functions (127,128). In this context the colloidal Au is useful 
because it renders visible cellular structures which would 
otherwise be invisible to the electron microscope. Electron 


microscopy has been used to study the growth of colloidal gold 
particles (129,130) and the most important and thorough work in 
this area has been by Turkevich et. al. (133,134,135). Recently 
electron microscope studies of the structures formed when 
colloidal gold aggregates have been undertaken. It has been 
determined that these structures are scale invariant or fractals, 
which can be described by a fractal dimension df = 1.75 - 2.05. 
These structures are in agreement with computer simulations in 
which the clustering of the particles is modeled as a diffusion- 
controlled process (131,132). 

The study undertaken here is similar to that of Turkevich 
et. al . (65,66) in the studies of gold hydrosols. 

The first study undertaken had as its object the investiga- 
tion of the effect of gold concentration on the particle size. 
Turkevich' s group reported that small HAUCI4 concentrations 
resulted in comparatively larger colloidal particles with a broad 
particle size distribution, and at higher HAUCI4 concentrations, 
the mean particle size decreased and the particle size distribu- 
tion narrowed. 

Our investigations on gold organosols revealed the reverse 
effect: a direct relationship between gold concentration and 
particle size. 

Turkevich's explanation for the inverse size/concentration 
relationship observed in his aqueous Au colloids is not directly 
spelled out, but it is evidently due to the belief that a certain 
critical concentration of reduced auric ions is necessary in 


order that they will agglomerate into a stable particle. Due to 
the statistical nature of physical events, this local concentra- 
tion will occur more readily in a concentrated solution, leading 
therefore predominately to nucleation rather than the slower step 
of particle growth. 

We believe that our opposite finding is a result of several 
factors. In the frozen matrix, nucleation and particle growth 
are probably favored about equally at the beginning. As the 
temperature of the matrix increases and it begins to melt, the 
single atoms and smallest particles are most mobile due to their 
small size. Collisions leading to particle growth are more 
common in a concentrated matrix, and thus the size increases. 
This dependence on particle growth is confirmed by the observed 
increase in polydispersity with increasing concentration. 

The effects of solvent viscosity and other factors are 
discussed in the next section. 

In our investigations with the electron microscope, several 
interesting features were revealed: First, the particles display 
no well-defined shape, in contrast with some of Turkevich's 
samples (66) which show either a trigonal, crystalline outline or 
a simple spherical shape. Secondly, our particles do not have 
similar optical density throughout: some areas of a single 
particle appear to be darker (have a higher electron cross- 
section) than others. It is interesting to note that, in those 
photographs which show the particles to be agglomerated, there is 
still space between the individual particles. This is believed 


to be the result of organic material adsorbed on the surfaces of 
the particles. This adsorbed material would have a much smaller 
electron cross-section than the gold of the particles themselves, 
and thus would be transparent. Further evidence for this adsorbed 
organic layer was given by our unsuccessful attempts to obtain 
SEM photographs of the gold samples. The samples were applied to 
the metal stages used and then the sample was coated with a 
vapor-deposited coating of gold (a standard SEM procedure for 
biological samples). Good photographs could not be obtained due 
to excessive noise levels emanating from the particles themselves 
but not the background. At the time, the operator attributed 
this to a capacitance effect produced when the organic-coated 
metal particle was again coated with metal, creating a spherical 
microcapacitor which had an inhibitive effect on the secondary 
electron emission. 



Gold / Acetone Colloid 

160,000 X 

1.8 X 10-5 g Au 

mL acetone 

mean particle size: 20 A 
median particle size: 20 A 






MEAN 20 8 
MEDIAN 20 8 


1.8 x I0' S 

B 26 38 51 6H 


FIGURE 2. Particle size distribution, MTF-82-S-01 



Gold / Acetone Colloid 

250,000 X 

2.7 X 10-4 = g Au 


mean particle size: 53 A 
median particle size: 50 A 










CC 20 




MEAN S3. £ 

GRAMS AU _ Zly , -4 

i — i 

20 40 60 80 100 120 !M0 160 


FIGURE 4. Particle size distribution, MTF-80-S-01 



Gold / Acetone Colloid 

250,000 X 

9.1 X 10-4 g Au 


mean particle size: 80 A 
median particle size: 60 A 



t !£• 

• ♦» 




K- 20 


MEAN 80 £ 


9.1 v 10 


D I 1 

20 40 60 80 100 120 NO 160 180 200 220 240 260 280 


FIGURE 6. Particle size distribution, MTF-82-S-02 



Gold / Acetone Colloid 

160,000 X 

5.3 X 10-5 = g A U 


mean particle size: 40 A 
median particle size: 38 A 



- 1 

# • 

+ r 

• • • 

* ' 

.. A •'• .^ 

# • 


* • • • • 




q Au = 5.27 X 10" 5 

mL acetone 

1 — 

MEAN = 40 A 
KEDIAN = 38 A 

13 2G 38 51 64 77 90 102 

FIGURE 8. Particle size distribution, MTF-112-S-01 

























10 20 30 40 50 





FIGURE 9. Concentration vs. Particle size, Gold Colloids: 
MTF-82-S-01, MTF-80-S-01, MTF-82-S-01, and MTF-112-S-01 . 


II. 3. Concentration Studies - Silver / Acetone 

These experiments were carried out in almost exactly the 
same way as those with gold. The "standard" warmup method was 
used (1 hour warmup under static vacuum with a cold, empty dewar 
surrounding the reaction vessel). 

The differences between gold and silver colloids formed is 
striking: while the color of the gold colloid solution is a very 
dark purple, the silver colloid solution is black. Also, the 
silver colloid is light sensitive. Samples which were exposed to 
the light would gradually turn a light gray, and the particles 
would precipitate as a spongy, gray mass after exposure to light 
for approximately 48 hours. Samples which were kept in the dark 
were stable indefinitely (up to 6 months). 

The electron microscope reveals even more striking differ- 
ences: the silver colloid particles are much larger than those 
of gold. It is also interesting to note the banded patterns in 
individual particles. At this time it is not known whether these 
striations are due to alternating layers of crystallites (each 
layer being the twin of the layers above and below it) or whether 
they are due to alternating layers of silver and organic material, 
The latter explanation seems more likely. It is not known 
whether the banded pattern is related to the light sensitivity of 
the colloid. 



Silver / Acetone Colloid 

250,000 X 

g Ag = 1.57 X 10-3 

mL acetone 

mean particle size: 258 A 
median particle size: 240 A 





8 Ag 

mL acetone 

MEAN - 258 A 
MEDIAN - 240 A 

- 1.57 X 10 

120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 

FIGURE 11. Particle size distribution, MTF-125-S-01 



Silver / Acetone Colloid 

250,000 X 

g Ag = 1.6 X 10-3 

mL acetone 

mean particle size: 376 A 
median particle size: 260 A 




8 Ag 
mL acetone 

MEAN - 376 A 

MEDIAN - 260 A 

1.6 X 10 


120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 

FIGURE 13. Particle size distribution, MTF-127-S-02 



Silver / Acetone Colloid 

160,000 X 

g Ar = 2.1 X 10-3 

mL acetone 

mean particle size: 316 A 
median particle size: 319 A 


20 ■ 

B *8 

mL acetone 

MEAN - 316 A 
MEDIAN - 319 A 

- 2.1 X 10 


co -* n 


FIGURE 15. Particle size distribution, MTF-113-S-01 




, 2.0 • 






" 1.5 • 






§ 1.0 





220 230 240 250 260 270 280 290 300 310 320 330 

FIGURE 16. Concentration vs. Particle size: 
MTF-113-S-01, MTF-127-S-02, and MTF-125-S-01 . 


Silver colloids showed a particle size dependence on concen- 
tration similar to that of gold. In these experiments, the 
concentrations of silver used were much greater than the amount 
of gold used in the previous studies of gold colloids, thus the 
particles were much larger. Since the silver sols were very 
polydisperse, median particle sizes were used in the correlation 
with concentration. 

Klabunde and co-workers have studied the clustering of metal 
atoms in organic solvent matrices extensively. The systems most 
studied were Ni/alkane and Co/alkane. In (149) it was reported 
that the use of a large excess of pentane over Ni (>300:1, mole 
ratio) resulted in the formation of very small (<30 A) nonferro- 
magnetic crystallites, while a smaller excess of pentane (<100:1) 
over nickel gave larger (780 A) ferromagnetic particles (particle 
sizes determined by soft x-ray scattering). In (148), Klabunde 
et. al. reported findings similar to these with respect to the 
question of f erromagnetism/nonf erromagnetism in small particles 
formed from nickel atoms co-condensed with various other alkanes, 
but reported no size differences; however, such differences may 
have been overlooked with the size determination method used (H2 
chemisorbtion and nitrogen BET adsorbtion isotherms, spherical 
particles assumed). Electron photomicrographs of similar samples 
showed the assumption of spherical geometry to be invalid for 
some of the samples (153). The present study supports these 
earlier findings. The crucial question to be answered for all 
these systems has to do with the mechanism by which the organic 


solvent moderates the clustering of the metal atoms and limits the 
clusters to a certain size. 

Some of the first work toward addressing this question was 
performed by Klabunde et. al. (153). This investigation revealed 
the morphology of small nickel particles formed from the warmup 
of different organic matrices to be different. 

In (154), Klabunde, Davis, Hattori and Tanaka discussed the 
factors influencing cluster growth from a metal atom/organic 
solvent dispersion. These factors are: (1) metal atom-solvent 
binding strength; (2) M2~solvent, M3~solvent, M4-solvent , . . .M( x ) 
solvent binding strengths; and (3) the viscosity of the solvent 
at the temperature at which the clustering takes place. M-M bond 
dissociation energy is not a factor since at these low tempera- 
tures, the clustering is probably irreversible. 

There is another factor involved, and that is the reaction 
of the metal clusters with the solvent molecules. This has been 
observed experimentally (148,149,154,155) by the recovery of 
fragments of the original organic solvent used from the dry metal 
powder. The effect of matrix dilution and varying warmup 
conditions suggests the existence of competing reactions: metal 
clustering and cluster reaction with solvent. Once a small 
cluster reacts with an organic molecule to form a strongly bonded 
organic fragment, that "coordination site" is no longer available 
for the addition of another metal atom or small cluster. Thus 
the reaction with solvent inhibits the growth of the cluster. 
This works the other way too: once the cluster has reached a 


certain size, it will be less reactive toward the solvent. The 
combination of these two effects limits the final size of the 
particles formed by encouraging a certain amount of nucleation 
and then moderating the growth rate until all the limiting 
reagent (metal) is used up. 

The situation for gold and silver sol formation is believed 
to be quite similar. 


II. 4. Concentration Studies - Copper / Acetone 

The copper/acetone system was not very amenable to study, 
and few experiments were carried out with it. In most instances, 
black colloid was formed initially, but one which turned olive 
green and flocculated in less than 12 hours. One very dilute 
reaction mixture resulted in a stable green colloid. An 
interesting observation with this sample was that addition of a 
small amount of H2O resulted in the formation of bubbles. A 
simple flame test revealed that the gas evolved was either H2 or 
CH4 . This same experiment was tried with the gold and silver 
sols, with the same result. 

No experiments were carried out to determine whether the 
color change and subsequent precipitation of the colloid was a 
result of light sensitivity, as was the case with silver. 



II. 5. Warmup Studies - Gold / Acetone 

Davis and Klabunde reported that for the co-condensation of 
nickel and alkane vapors, a temperature staged (slow) warmup of 
the frozen matrix formed a nonf erromagnetic metal powder with 
crystallite sizes of < 30 A, whereas a direct warmup of the 
frozen matrix resulted in the formation of larger (> 80 A) 
ferromagnetic crystallites (149). 

The experiments performed for the gold/acetone colloid syste 
support this earlier work. It was found that, without exception, 
a fast (< 1 hour) warmup resulted in the formation of a flocculent 
purple/gold mass that was definitely not colloidal, small gold 
crystallites being visible. However, experiments with tempera- 
ture-staged warmups always resulted in stable gold sols. 

A series of organic solvent slushes, methanol/liquid N2 
(-95 C), ethanol/liquid N2 (-117 C) and pentane/liquid N2 
(-130 C) were placed around the reaction vessel and left in place 
for one hour, at which time they were removed and a cold, empty 
dewar which had contained liquid N2 was placed around the reactor 
and left for one hour. During this procedure, a static vacuum 
was maintained over the warming matrix until meltdown was 
complete. A similar series of experiments was also performed in 
which the slush baths were left around the reactor overnight. 

No clear-cut trend relating warmup temperature to particle 
size was established, other than the general trend stated above. 


The explanation proposed for the lack of evidence for such a 
trend involves the difficulty of controlling the metal/acetone 
ratio in the matrix. As was seen in the previous sections, the 
metal/acetone ratio also has an effect on the resulting particle 
size, and this must be held rigidly constant in any experiments 
on the effects of temperature staging on particle size. 



Gold / Acetone Colloid 

250,000 X 

g Aii = 5.6 X 10-4 

mL acetone 

Warmup conditions: pentane/LN2 
slush overnight 

mean particle size: 48 A 
median particle size: 40 A 






WARMUP CONDITIONS: pentane/ LN slush overnight 
CONCENTRATION: g Au 5.6 X 10~ 4 

mL acetone 

MEAD - 48 A 
MEDIAN - 40 A 

20 40 60 80 100 120 140 160 180 200 

FIGURE 18. Particle size distribution, MTF-89-S-01. 



Gold / Acetone Colloid 

250,000 X 

g Au = 9.6 X 10-4 

mL acetone 

Warraup conditions: ethanol/LN2 
slush overnight 

mean particle size: 34 A 
median particle size: 40 A 


•* ""* 

» • . • 

% W m 

.: % 





WARMUP CONDITIONS: ethanol/ LN slush overnight 

CONCENTRATION: r Au - 9.6 X 10~ 4 
ml acetone 

MEAN - 34 A 
MEDIAN - 40 A 

-I I I I L. 

20 40 60 80 100 120 140 160 180 200 220 240 

FIGURE 20. Particle size distribution, MTF-90-S-01 



Gold / Acetone Colloid 

250,000 X 

g Au = 9.3 X 10-4 

mL acetone 

Warmup conditions: methanol/LN2 
slush overnight 

mean particle size: 60 A 
median particle size: 60 A 


wi. ''Hi 



WARMUP CONDITIONS: methanol/ LN, slush overnight 


mL acetone 

MEAN - 60 A 
MEDIAN - 60 A 

9.3 X 10 

20 40 60 80 100 120 140 160 180 200 

FIGURE 22. Particle size distribution, MTF-91-S-01 



Gold / Acetone Colloid 

250,000 X 

g Au = 2.5 X 10-3 

mL acetone 

Warmup conditions: pentane/LN2 
slush, one hour 

mean particle size: 68 A 
median particle size: 60 A 






UARMUP CONDITIONS: pencane/ LN slush, one hour 
CONCENTRATION: g Au - 2.5 X 10 _3 

ml, acetone 

MEAN - 68 A 
MEDIAN - 60 A 


20 40 60 80 100 120 140 

160 180 200 220 240 

FIGURE 24. Particle size distribution, MTF-88-S-02 



Gold / Acetone Colloid 

250,000 X 

g Au = 6.5 X 10-4 

mL acetone 

Warmup conditions: ethanol/LN2 
slush, one hour 

mean particle size: 48 A 
median particle size: 40 A 






» i 




* ♦ 





UARMUP CONDITIONS: ethanol/ LN alush, one hour 


8 Au 

mL acecone 

- 6.5 X 10 

MEAN - 48 A 
MEDIAN - 40 A 




60 80 100 120 140 160 

180 200 

FIGURE 26. Particle size distribution, MTF-86-S-01. 



Gold / Acetone Colloid 

250,000 X 

g Au = 5.4 X 10-4 

mL acetone 

mean particle size: 38 A 
median particle size: 40 A 


% • 





UARMUP CONDITIONS: methanol/ LN slush, one hour 


8 Au 

- 5.4 X 10 

mL acecone 

MEAN - 38 A 
MEDIAN - 40 A 

20 40 60 80 100 120 140 160 180 200 

FIGURE 28. Particle size distribution, MTF-88-S-01 


II. 6. Spectroscopic Studies - Gold / Acetone Sols 

A. UV-visible 

UV-visible spectra were recorded for gold sols only. The 
absorptions attributed to the gold sol particles occurred at 706 
nra and at 572 nm. The absorption at 572 nra was attributed to 
plasraon absorption by the conductive particles (136,137,138). 

Visible absorption spectra have been used as a method of 
determining particle size in gold colloids, smaller red particles 
absorbing in the range 500-550 nm and blue sols absorbing in the 
range 580-650 nm (for aqueous sols) (139,140). Jeppeson and 
Barlow reported that a red gold colloid absorbed at 525 nm. 
Electron microscopy revealed that the particles formed were 
smaller than 40 A (141). This method is not a foolproof way of 
obtaining particle size, however. The color of the sol is very 
sensitive to such things as the concentration of reagents used to 
make it, pH, electrolyte additions and additions of adsorbed 
substances such as proteins (142,143,144,145). 


II. 6. Spectroscopic Studies - Gold / Acetone Sols 
B. Nuclear Magnetic Resonance 

The solvent (acetone) was evaporated from a gold colloid 
under vacuum and collected in a trap at 77K. The lH NMR of this 
solvent showed only a singlet due to the six equivalent hydrogens 
on acetone. No other species were detected, even when the 
acetone peak was blown up until it was off the scale. 






1 1 -9 





































4 74 5 



8H PO 














-1 . 


HZ/CM 133. 












pf :i 

FIGURE 29. iH-NMR spectrum of acetone 

removed from gold colloid solution 


RCtroNt orrtR reschon «uth ou 



FIGURE 30. Appearance of Figure 29 magnified 128 times 


II. 7. Electrophoresis - Gold / Acetone Sols 

The phenomenon of electrophoresis, the movement of charged 
particles or macromolecules in response to an electric potential 
was discovered by Reuss and reported in 1809. He thrust two 
glass tubes into a lump of moist clay, placed a layer of sand in 
the bottom of each tube, and filled the tubes partially with 
water. He then applied the direct current generated by 74 
silver/zinc cells across the clay by means of electrodes immersed 
in the water. The positively charged side of this system became 
cloudy due to the migration of negatively charged particles 
through the sand layer. The water in the negatively charged side 
rose, demonstrating the phenomenon of electro-osmosis (164). 

Picton and Linder studied the movement of the boundaries of 
colloidal AS2S3, shellac, Fe2C>3 and hemoglobin solutions confined 
in a U-shaped tube and subjected to a direct current. They 
reported that reversal of the current reversed the direction of 
the migration (165,166). 

Hardy showed that negatively charged denatured colloidal egg 
albumen could be made positive by the addition of acid. The 
concentration of acid needed to reduce the particle's mobility to 
zero was called the "isoelectric point" (167). 

Svedberg and Tiselius extended the utility of this method 
for the separation of proteins, by the use of ultraviolet 
radiation which made the proteins fluoresce. This fluorescence 


could then be photographed, and intensity measurements made at 
various points in the apparatus allowed a quantitative estimation 
of the boundary positions of different proteins (168). 

Prideaux and Howitt noted that when albumin, gelatin or 
casein were adsorbed upon gold sols, the electrophoretic 
velocities of the sols matched those of the neat proteins (169). 
This observation pointed to the importance of the colloidal 
particles' surface condition in the electrophoresis experiment. 
Prideaux and Howitt exploited this finding by electrophoresing 
various agar sols which were rendered visible by the addition of 
a purple gold sol (170). 

Tiselius ushered in the era of preparative electrophoresis. 
He constructed the familiar U-tube apparatus from rectangular 
glass curvettes that were joined by flat ground glass surfaces. 
A desired protein fraction (for example) could be isolated from 
solution after electrophoretic separation merely by sliding out 
the section of the apparatus containing that fraction (171). 
Preparative electrophoresis is now a widely-used technique, 
especially in the biological sciences. Nowadays it is generally 
carried out on paper sheets or gel films rather than in solution. 

Philpott developed a cylindrical lens optical system which 
improved the location of boundaries between components in an 
electrophoretic separation by displaying them as peaks. An added 
benefit of this system was that the relative concentrations of 
the components were reflected by the peak heights. This lens 
system also found use in ultracentrif ugation (172). 


-Pt electrodes 


filler tube 


PATH LENGTH - 223 mro 

pyrex glass construction 

FIGURE 31. Diagram of electrophoresis cell used for 

determination of electrophoretic velocities 


In the present study, experiments were carried out in a 
U-tube apparatus similar to that described by Burton (173). Neat 
acetone was placed in the U-tube, until the limbs were approxi- 
mately half-full. The gold/acetone colloid was run in under the 
neat acetone by means of a stopcock in the bottom of the U-tube, 
carefully so that a sharp boundary was maintained between the 
clear acetone and the dark purple colloid. Next, platinum wire 
electrodes were placed in the top ends of the tube, and a direct 
current applied across them. The boundary was marked at the 
beginning of the experiment, and again at the end, and the 
distance and time recorded. 

The raw data for the electrophoresis experiment is recorded 

Sample # Electrophoretic Velocity toward (+) electrode 

MTF-90-S-01 (gold/acetone) 1.7 /VS 

MTF-91-S-01 (gold/acetone) 2.2 ^/S 

MTF-86-S-01 (gold/acetone) 1.2^/S 

The relation between electrophoretic mobility (the electro- 
phoretic velocity divided by the potential gradient) and the 
surface properties of the particle (usually modeled as an ionic 
double layer for aqueous colloid systems) is a classical problem 
in colloid science. The Helmholtz-Smoluchowski equation can be 

U = c 3 
X hrrtj 

considered as the oldest solution to this problem. In this 



U ■ electrophoretic velocity 

X = strength of the applied dc field 

J = electrokinetic potential 

G = dielectric constant of the medium 

n = viscosity of the medium (Stokes) (174) 

The validity of this expression has been long known to be 
rather restricted, and much refinement has been carried out. In 
1924, Hueckel published a detailed calculation of the electro- 
phoretic retardation force, which can be thought of as analogous 
to the retardation force which develops in an electric motor to 
counter the applied force. On the basis of this modification, 
Hueckel came up with the following modified equation (175): 

U = e $ 
X 6rr « 

The apparent contradiction between these two expressions was 
resolved by Henry, who took into account the deformation of the 
applied dc field by the presence of the particles. This expres- 
sion was originally derived for an insulating particle, but there 
is strong theoretical evidence (supported by experiment) that 
even metallic particles can be treated as insulators in electro- 
phoresis (176). Henry's expression is: 

JL = ۥ J f. (ka) 
X 6 1Y rj 1 

The dimensionless product ka is a measure of the ratio between 
the particle radius and the thickness of the (ionic) double 


layer. In the limit ka->oo(when the double layer is very thin 
compared with the radius), f\ (ka) = 3/2 and the result is the 
Helmholty-Smoluchowski equation. In the limit ka -*■(), f^ (ka) = 1 
and Hueckel's result is obtained. 

Application of any of these expressions to the gold/acetone 
colloid system poses a number of problems. First of all, these 
equations are all predicated on the DLVO theory of stabilization 
for colloidal particles, in which the formation of a tightly 
adsorbed layer of ions is supposed to account for the charge on 
the particle, and an outer, more loosely attracted layer of 
counterions stabilizes the particle in solution by repelling the 
similarly charged outer layers of other particles, preventing 
coagulation (177). Although the gold/acetone system must contain 
some kind of positively charged species to preserve electrical 
neutrality and to allow electrophoresis to occur, the nature of 
this species is unknown, as is the nature of the charged particle 
interface. Also, the theoretical models have usually been tested 
in aqueous systems. Their validity for non-aqueous systems 
(different dielectric constant, different viscosity) is unknown. 
One serious difficulty in all the theoretical models is that of 
the two quantities which they relate, ^-potential and electro- 
phoretic mobility, only one, the electrophoretic mobility, can be 
directly determined, ^-potential can be determined by other 
methods, for example by streaming potentiometry , but the theory 
here shares many features of electrokinetic theory, and therefore 
methods for determination of 3 -potential are not completely 



The Hueckel equation for small ka is the one most likely to 
be applicable to electrophoresis in non-aqueous media (184): 

U = G J 

solving for $ : 

T = U 6 rf n 
J x e 

For the gold/acetone system the values are: 

10 = kinematic viscosity of acetone = 0.400 centipoise (178) 

X = potential gradient for U-tube = 0.568 V/cm 

C =■ dielectric constant for acetone = 20.7 

Solving for the three samples tested obtains the following 

MTF-90-S-01 3 = -840 mV 

MTF-91-S-01 5 = -1080 mV 

MTF-86-S-01 "?= -590 mV 

These values are much higher than those usually reported for gold 
sols in aqueous solution (180). 








x 10" 


3 (mV) 


Colloidal gold 



Whitney & Blake 

Colloidal gold 




Pt sol 



Whitney & Blake 

Pt sol 




Colloidal Pb 




The reasons for these great deviations are at present 
unknown, and it is unknown whether these are true values or if 
this is a case where the generally accepted equations do not 
apply. It is also possible that our experiment set-up was too 
crude to produce good results, but as was stated above, the 
design is very similar to that which Burton used to determine the 
5" -potential for gold sols in the table above. 

It is possible to calculate the charges on the particle from 
the 3 -potential by the following expression. 

3 = _e in - r ) 

E r ri 


e = charge (coulombs) 

r^ = radius of particle and tightly adsorbed ionic layer 

r = radius of particle 

E = dielectric constant of the medium 

For the gold colloid system, we can calculate the charge on 


the individual particles, assuming the value (r^ - r) to be 3 A: 

e = E n r C? 
Tn - r) 


Sample # av. particle size, A charge, coulombs 
MTF-90-S-01 34 A 7.3 X 10-7 

MTF-91-S-01 60 A 2.8 X 10-6 

MTF-86-S-01 48 A 9.9 X 10-* 

The origin of the particle's charge is presently unknown. 
It may be due to some unknown capacitance effect associated with 
the metal atom reactor, although Klabunde and co-workers' 
experience with the formation of small nickel and cobalt particles 
seems to rule this out (148,149). Although the nickel and cobalt 
particles are of colloidal dimensions, there apparently exists no 
mechanism for stabilizing them in solution. 

Henglein and co-workers and Meisel and co-workers have 
reported that for systems of aqueous gold colloids containing a 
small amount of acetone and 2-propanol, gamma irradiation by "^Co 
produced free radicals which transferred an electron to the 
colloid particle. This electron had a high enough potential to 
reduce H2O, and its transference to the gold particle extended it 
lifetime so that it could react with H2O in a diffusion-controlled 
way. In effect, the gold colloid catalyzed the reduction of H2O 
by the acetone free radical (156,157,158,159,160,161). It is 
known that free radicals can be formed by high temperatures and 


trapped in frozen organic matrices (162,163). Under our experi- 
mental conditions, radicals could be formed in the gas phase by 
contact with the hot crucible, then trapped by the cold matrix on 
the reactor walls. Warmup would then release these free radicals 
to transfer their electrons to the metal clusters. 

It is also possible that the charge is formed by static 
electricity. This was proposed by some of the early authors on 
the subject (167). 


II. 8. Miscellaneous Observations - Metal Sols 

Conductance Measurements 

The conductance of various gold/acetone colloids were 
measured and compared with neat acetone, as well as various 
concentrations of Nal in acetone and in a gold/acetone colloid. 


Neat Acetone 










1.5 M Nal/Acetone 

0.15 M " " 

0.015 M " " 

0.0015 M " " 

0.075 M NaI/MTF-88-S-02 

0.0075 M Nal/ " " 

0.00075 M Nal/ " " 


Conductance (M ohms ~1 cm~l) (23 C) 
A. 5 

not enough sample 

These experiments were undertaken to understand the nature 
of the counter ions that the electrophoresis experiment indicates 
must be present. The fact that the colloids' conductance is 
approximately the same as that of neat acetone indicates that 
this counterion must be present in extremely tiny amounts, or 
perhaps it is only formed when the direct current is applied. In 
light of the very small potential gradient used, however, this 
seems unlikely. 


Temperature Sensitivity 

A small sample of gold/acetone colloid was placed in a test 
tube heated in an oil bath from 23 °C to approximately 150°C (at 
which point it was boiling). Another sample was placed in a test 
tube and placed in a beaker of water at 19 °C and this placed in a 
refrigerator and cooled to 3 C. This test tube was then placed 
in liquid nitrogen and the colloid frozen solid. This was then 
allowed to thaw at room temperature. Both samples remained as 
stable sols after return to room temperature, and remained stable 
indefinitely. This is evidence for polymer stabilization (151) 
since charge-stabilized gold colloids always precipitate when 
subjected to freezing or boiling (182). 

Addition of Water 

A curious phenomenon was observed upon the addition of a 
small amount of water to either the gold/acetone, silver/acetone 
or copper/acetone sols. Bubbles were evolved which a simple 
flame test revealed to be either H2 or CH4. This phenomenon 
ceased after a certain amount of water was added, and the colloid 
then precipitated. It is difficult to explain this. Henglein 
and co-workers reported that the free radicals generated by "^Co 
Y-irradiation of acetone in an aqueous gold colloid would reduce 
water to form H2 (156-161). The presence of similar radicals in 
the gold/acetone colloid system transferring electrons to the 
gold particles could account for those particles' charge. These 
electrons would then be available to reduce water when it was 


added. We have no direct evidence for radical formation, however. 

Light Sensitivity - Silver/Acetone Sols 

All the silver/acetone sols investigated were initially a 
dark black or purple/black color. After 3-4 days exposure to 
light, they gradually turned gray and the metal precipitated as a 
spongy light colored mass. When the colloids were kept in the 
dark however, they retained their dark color and remained stable 
indefinitely (up to six months). This phenomenon needs further 


II. 9. Film Formation - Gold / Acetone Films 

Elemental Analyses 

Samples were prepared for elemental analysis by removing the 
solvent under vacuum into a cold trap. The dry residue was 
subjected to a dynamic vacuum of approximately 5 X 10 - 3 mm Hg for 
approximately one hour at room temperature to remove all traces 
of solvent. The resulting dry residue was then scraped from the 
Schlenk tube into a small vial and sent to Galbraith Laboratories 
for metal, carbon, and hydrogen analyses. Oxygen was determined 
by difference. The results of analyses are summarized in the 
following table. 


% c 

% H 

% Metal 


(by difference) 



82.78 (Au) 




62.81 (Au) 




81.45 (Au) 


Sample # 




MTF-130-S-01 0.62 <0.01 (Ag) (not enough sample for 


Except for MTF-130-S-01 , these were all mixed samples, that 
is, they contained material from several different reactions; 
therefore no general trends regarding concentration can be found. 
Klabunde and co-workers found that for Ni and Co co-condensed 
with various organic solvents (pentane, hexane, toluene, THF, and 
heptane), either slow warmup conditions or a large excess of 


organic species resulted in the incorporation of more carbon and 
hydrogen in the resultant powder (112,113,114). It is very 
likely that this same effect is operative for the metals in this 
study, especially since a correlation between matrix concentration 
and particle size similar to that noted in (112) was also observed 
in the present study ( vide supra ) . 


11.10. Pyrolysis / G.C. - M.S. - Gold / Acetone Films 

Klabunde, Davis and Severson (148,149) reported the 
incorporation of alkane fragments in nickel and cobalt powders 
formed by vacuum deposition of these metals in cold alkane 
matrices. In their experiments, it was found that the alkane 
(pentane, hexane, heptane, octane and 2,2- and 2 , 3-diraethylbutane) 
was cleaved into smaller hydrocarbon fragments as a result of 
reaction with small growing metal particles. ESCA ion-beam 
etching experiments revealed the carbon to be present as sp2- and 
sp3- hybridized forms dispersed throughout the small metal 
particles (148). Pyrolysis experiments on the nickel powders 
revealed that only CO2 , CH4 and H2 were evolved upon heating to 
600°C. C0 2 was evolved between 150 and 300 °C. Above 300 °C, only 
CH4 and H2 were evolved. 

Products evolved by hydrogenation and hydrolysis of the Ni- 
pentane powder were very similar, and the product distributions 
from these experiments were also very similar (149). Products 
found were CH4 , C2H5, C^H^o. and C5H12. No species containing 
more than five carbons were found. From these experiments, it 
was concluded that the pentane fragmentation occurred during the 
codeposition - warmup procedure and not during the product 
workup . 

The results obtained through pyrolysis/mass spectrometry of 
the powders obtained by solvent evaporation from the gold/acetone 


and silver/acetone samples stand in contrast to these earlier 
results. The gold powder was pyrolized in a Pyrex glass tube and 
the volatile products evolved were inlet directly into the mass 
spectrometer. The temperature was gradually raised from room 
temperature through 300 °C, and the mass spectrum recorded at 
regular intervals. The most striking thing about the products 
evolved was their high molecular weight, and the presence of 
repeating units of 12, 14, 15, and 17 daltons indicating the loss 
of carbon, -CH2, CH3 and -OH groups. 

The open, low pressure pyrolysis equipment used seems to 
preclude the polymerization or oligomerization of acetone during 
the pyrolysis experiments, rather, it seems that the high 
molecular weight products are formed during the matrix 
codeposition-warmup procedure. It seems that these high molecular 
weight products formed are of varying sizes, so exact characteri- 
zation seems to be out of the question. The best we can hope for 
is to identify functionalities. More detailed infrared data is 
needed for this. 

The above interpretation of the pyrolysis/M.S. experiment is 
supported by the literature on polymer stabilization of colloidal 
particles. As was discussed in the Historical section, colloids 
are stabilized in solution in one of two ways: either by the 
absorption of ionic species in solution in the form of double 
layers, relying on electrostatic repulsions to stabilize the 
particles, or by absorption of lyophilic high molecular weight 
molecules such as starches, proteins, gelatins, PVA, etc. (in 


aqueous solution) (150,151,152). The role of these so-called 
"protective colloids" is reviewed in the Historical section ( vide 
supra ) . 

The mass spectra obtained from the pyrolysis/M.S. experiment 
for the gold/acetone colloid are reproduced on the following 

It is evident that the amount of volatile organic material 
given off peaks at about 240 - 300 C, and decreases at higher 




I,, ij ji , , iBhS jjjl i kniiL l .k L 

l«S. 1 

~» ■ »s 

lee. * -i 

355. I 

4B1.C <2C.7 «.£■ 




r nie« 

" ' ^ ' 


FIGURE 32. Mass spectrum of gold colloid film powder 
pyrolyzed at 80 °C, directly into M.S. 



'El IS ' ?~ C C 

71 1 

. » ■ I " tt l " 

IH.I -i 

..ill itk, 9 :^ 

IO.I !'?•■ 

■*'■ , ' ■ ■■ 

199.9,.. S2I. I 

-IL, , 7K , 3 

.9 4I 9. 1 ««6. I 


FIGURE 33. M.S. of gold colloid film powder 
pyrolyzed at 150 C. 


n~ii SPECIfcun 


es.i ei.i 

i.ill l lll. i jlllli 


i. Muni mii,|- 


132. I !<?- ' 

r 4 net. 

«"£ aee jsf 

■<^i.; ;im.<: <.2s,.fr — ,MS.y 

FIGURE 34. Gold colloid film powder pyrolyzed at 240 °C 


r»«SS 3PECT»u« 

31 . I 

"j 1 "V .i. 19 ?- 1 122-1 

II , b3. 1 O*. I II 

143.8 |6;. 9 193.8 L 223.8 



ee.e - 







se.e - 



■= r-4=-i 



429.8 443.^ 

, — r-ia^, 

> , II 

FIGURE 35. Gold colloid film powder pyrolyzed at 300 °C. 


11.11. Pyrolysis / G.C. - M.S. - Gold / Acetone Films 

In an effort to gain more understanding of the nature of the 
organic material adsorbed onto (or incorporated into) the colloid- 
al gold particles, an experiment similar to the one outlined in 
the preceding section was performed, with the exception that a 
closed-tube pyrolysis apparatus was used, and the volatiles 
evolved during heating the sample were then swept into a G.Ci 
column (six foot Porapak Q) with He gas. These products were 
characterized by mass spectrometry upon elution. 

Under the conditions used in these experiments, high 
molecular weight organics are probably broken down by the combina- 
tion of high temperature and pressure in the closed pyrolysis 
tube. The important thing to note is that many of the organic 
molecules evolved contain more carbon atoms than the original 
material, acetone. This stands in direct contrast to the earlier 
reported work of Klabunde et. al. on the organic molecules 
evolved in the hydrogenation or hydrolysis of Ni/alkane powder, 
which were never observed to contain more carbon atoms than the 
starting alkane (149). This is further, indirect evidence for 
the formation of high molecular weight organics from the acetone 
present in the frozen matrix. It is important to note, however, 
that there is no direct evidence for the presence of such species, 

The data from the chromatograms and mass spectra for both 
the gold/acetone and silver/acetone colloid film powders are 


summarized in the following table. 


MASS SPECTRA: el, 35 eV 

Column Species Observed 

Sam pie , Conditions Temp. Program (in order of elution) 

Au film powder, At I + 6.2 min CH4, CO2 , C2H4, H2O, C3H6, 

pyrolyzed 8 min @ T — > 100 °C. CH3OH, C4H4, C3H8, C3H7OH, 

180 °C At I + 35 min C4H8, CH3COCH3 

injected 20 s. T — > 150°C. 

Porapak Q 6' long 

Au film powder, Same as above. C 4, CO2, C2H4, H2O, C3H6, 

pyrolyzed 30 min CH3OH, C4H4, C3H8, C4H8, 

@ 250 °C another C4H8, CH3~C=N(?), 

injected 20 s. CH3COCH3 

Au film powder, Same as above. CH4 , CO2, C2H4, H2C0(?), 
pyrolyzed 23 min H2O, C3H6, C4H4, C3H8, 

@ 360 °C C4H8, another C4H8, 

injected 20 s. CH 3 C5N(7), CH3COCH3 

Ag film powder, Same as above. CO2 , H2O 
pyrolyzed 8.8 min 
@ 180 °C 
injected 20 s. 

Ag film powder, Same as above. CO2 , C2H4, 03115(7), C4H4 , 

pyrolyzed 1 hour @ C3H8, ^4^8 

250 °C injected 20 s. 

(Some noise in spectrum 

due to contact between 

column and furnace) 

Ag film powder, Same as above. CO2, C2H4, 03115(7), C4H4, 
pyrolyzed 9 min @ C 3H8» C4H8, CH3COCH3 

360 °C 
injected 20 s. 

Au film powder w/ Same as above. CO2 , H2O, C3H5, C4H4, 
several drops d5~ C3H8(?), C4H8, another 

acetone added, C4H8. (no deuterated 

excess allowed to species observed) 

evaporate, pyro- 
lyzed 8 min @ 180°C. 
injected 20 s. 


Sample , Conditions 

Same sample as 
above, pyrolyzed 
30 min @ 250 °C. 
injected 20 s. 

Same sample as 
above, pyrolyzed 
23 min @ 360 °C. 
injected 20 s. 

TABLE 8 (continued) 
MASS SPECTRA: el, 35 eV 

Temp. Program 

Same as above, 

Same as above. 

Species Observed 

(in order of elution) 

C0 2 , C 2 H 4 , C 3 H 6 (?), C4H4, 
C 3 H 8 , C 4 H 8 , CH3COCH3 (no 
deuterated species 

C0 2 , C 2 H 4 , H 2 0, C 3 H 6 , 
C4H4, C 3 H 8 , C4H8, CH3COCH3, 
(no deuterated species 

It is interesting to note that the silver colloids contain 
much less organic material than the gold colloids. Since there 
is a higher metal/acetone ratio in all the silver colloids 
prepared, this is not surprising. Klabunde and co-workers noted 
that Ni/pentane powders in which the Ni/pentane ratio was high 
contained less carbon and hydrogen than those powders in which 
the corresponding Ni/pentane ratio was low (149). This effect 
was also noted for cobalt (148). The reason for this is not 
clear, but it probably has to do with the competition between 
metal particle growth and metal particle reactions with the 
organic solvent molecules initially present. 


11.12. Infrared Studies - Gold / Acetone Films 

Infrared spectrophotometry of the dry gold colloid residue 
(acetone removed under vacuum) yielded some useful information. 
The dry residue was ground with dry KBr powder and then compressed 
into a pellet. Due to the very weak absorbances, the desired 
regions of the sample were scanned numerous times, and the 
absorbances added together by the computer data station (Perkin- 
Elmer 1330). Due to limitations on the computer's memory space, 
only portions of the spectrum could be repetitively scanned in 
this manner. 

Perhaps the most important observation was that of a gold- 
carbon stretch at 570 cm~l. The only gold-carbon stretching 
frequencies reported in the literature are for mononuclear gold 
(I) and gold (III) compounds in which the carbon is present in 
the form of a methyl group. Nonetheless, there seems to be good 
agreement and it is not evident that there are any other possi- 
bilities to which this absorbance can be attributed. Puddephatt 
reports that Au-C stretching frequencies (for methyl groups) 
range from 457-591 cm~"l , depending on other ligands present 
(146). Nakamoto lists three Au-C stretches (147): 

Compound x) (Au-C) , cm" 

[(CH 3 ) 2 Au Cl] 2 571, 561 

[(CH 3 ) 2 Au Br] 2 561, 550 

[(CH 3 ) 2 Au I] 2 550, 545 


The IR spectra are reproduced on the following pages, along 
with their assignments. 

It is evident from this data that there is a significant 
amount of organic material incorporated with the gold colloid 
particles. Even vacuum pumping on this material for up to one 
hour at pressures as low as 20 mm Hg failed to remove it. We can 
also conclude that at least some of this material is chemisorbed 
rather than physisorbed on gold, due to the presence of a 
gold-carbon stretch in the IR. 


2 5 









— - 

— i 1 


i » 





i i i 
— — i — 


'. . ...' 

. — ' 

-i i_ 


i ' 


— 1 — , 




=1 J- 

" i :■ 

.: . 

■i _ 


_ . 





■ : r- 


- 1 ' 

■'--! j 80 7 





— = 



/ 1 

" ?M : -mu 

: :r:t:: 


■ : : 

-_r- r '~ 

■: "j: i - i\ 

: - 1 

.. i :. 

i: i :•/! b= 


! : . /; 

60 1 J i 

- --1 -: =| -•. : 60 1 

~j -=f==l: \ 

.--.!: 1 / 

:.■ . 

- -i- — ] — — 


1 1 \ 

■ - j —r-JTrz — •}= 

■- ;! -:\r-~ 

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l: : ! / ' I \ 

. r/i - ; l ; 

i i --_.}. :-r r 

i ; \ 


1 j i 

- i - | --•■' ' 


■ , • j 1 

/ ! ; i '1 

i i 

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i / ■ i 

! ■ ■ ! . :; 


! / 


: : ;j | 

; : ! 1 


/ : 


-=rj: , ■ 

: ' 


j j 

- \r~ 



i r 


= ; :^ ; 1 

■ - . - 

i\ / ; 

i : j ■ ■ i m 


— t 

: :;.::-. 

i \ / 

\ ■ .'■ ' : 


-1-; -■! i , vy i . i 

: : ! • : : • ; 1 - -"-: j=r: 

: ~: J==li=?!:=rl 



*?*- -dS^ 

3Q0SA - *<:<:«.. 



FIGURE 36. IR spectrum of gold colloid film powder, 
3420 cm" 1 = 0-H (water) 
2960 era" 1 = -0 C-H 
3040 cm" 1 = -J C-H (olefinic) 



i i i i 

1 1 





1 1 



i 1 

i i 

_l L. 

, , 

tL _p_ 


— :- 

r -£EzL 



: : ■ 


r— -J 

..... L. ,~ 


^z:N: : 





— . 




: :":. 

■=-: r ; 

- - 

.. - 



— : 



. ' ~ 

• : ■:-" 

: - T - 

: i; .1 i^:: 

: [.:::. 

.1 . 

i - ■ 

1 ■ : 


[ - — - 

- t- - 

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f i 

i :.-_tj | ..:-- 

-_-_-_ u. . 





: i - ' 
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. i V • " 

=—/(•: / 


■■-■1 ■■ 

: 1 : . ' : 
- 1 



i- i== 


:: 1 :: : 

:i ; '■ 

: i :::::. 

_' : 

: : 1 : 

j - 

/ r 




r ' i 

. : . 1 . 

" ! 


l ' / 

■ : ■ j 

■. j ( - 

: -; 


\ / 

. : . J : . - 

! . . . . 


1:. . 

" I * " 

\ ■ / 

- 1 

: --S. r : 2 

:^ - _: 

M = 


■:\4\ ;L 

- ' ~. 


":^!- ; -: : 



: l^=== 

■ "— i - . . . 


=j i- - 

~- :": = 


:: j ".: 

i^i': '.: 

: rzrf— -.- 

• L'|--~ 




i i . 

13 20 25 

. . i . . . 


. : -:. 



=i=r|! --;. 


= ;-:!/ 

!=rr]: : -:r? 

:— T 


: . . i 

^:-;| -i 

I : : : ; 

- • : .' 



• / i ~ - 


/i - 

: : ■ ' 

/ 1 

:-: ■- : 

' i - i 

: : v. 

~:.. :, 


1. _: 

j - . - 

V '/ 

. ■ i : . 










-: H - ! : 

i 1 

i ; 

i i 

^ . i 






FIGURE 37. IR spectrum of gold colloid film powder, 
1760 cm" 1 = x) C=0 
1620 cm -1 = C=C 
570 cm" 1 = Au-C 


11.13. General Conclusions 

The gold/acetone, silver/acetone and copper/acetone sols 
described in this thesis appear to be stabilized by a combination 
of adsorbed organic material and an accumulation of electrons on 
the particle. The process responsible for the formation of the 
organic material is probably also the moderating reaction which 
slows down the clustering of metal atoms such that small particles 
are formed rather than a mass of metal. This clustering process 
is affected by the concentration of metal atoms and the warmup 
conditions imposed on the frozen matrix, a slow warmup and/or 
small concentration of metal atoms favoring the formation of 
smaller particles. These sols are extremely stable, samples 
exhibiting stability for over 1 year. 



Surface-enhanced Raman scattering would seem to be the tool 
most applicable to study of the absorbed organic material on the 
surface of the particles. Such a method has been used for the 
study of materials absorbed on the surfaces of aqueous gold 
colloids, including probing the nature of electron donor and 
acceptor sites and specific absorption of TTF and TCNQ on a gold 
colloid surface (183). 

The light sensitivity of the silver colloid clearly needs 
further investigation. This process appears to be slow enough 
for kinetic and quantum yield studies, and it would be interestinj 
to find out if the silver colloid is sensitive to specific 


IV. 1. Equipment and Parameters 

Metal vapor reactions were carried out in a reactor composed 
of a top and bottom which are commercially available from Kontes - 
Martin Glass Company. The reactor bottom was a three-liter glass 
resin kettle (Kontes part no. 61200) which was mated to the 
reactor head (Kontes part no. 613200) by a 4 1/4 inch ground 
glass flange. The top also has four 24/40 standard taper ground 
glass joints of which two serve for the introduction of water 
cooled hollow copper electrodes. The other two are used for 
product recovery, attachment to a vacuum system, and for intro- 
duction of the solvent vapor (See diagram). 

The vacuum line was of a standard configuration, and included 
both fixed and demountable solvent traps, a vacuum/inert gas 
manifold, mercury manometer, and thermocouple pressure gauge 
(Arthur F. Smith & Co.). All valves were of the greaseless, 
teflon and glass type (J. Young Ltd.). Two oil diffusion pumps 
and two mechanical vacuum pumps (Sargent-Welch Co.) complete the 
vacuum system (See diagram). 

Electron photomicrographs were obtained with either a 
Hitachi HU-11B transmission electron microscope or a JE0L JEM-100C 
transmission electron microscope. Negatives were produced and 
developed by Mr. Larry Seib of the KSU Physics Department. 


FIGURE 38. Diagram of vacuum system and metal ato 

ra reactor 


Prints were made by KSU Photo Services. 

Ultraviolet and visible spectra were collected on a Cary-14 
spectrophotometer . 

Proton NMR spectra were obtained on the Chemistry Department 
Bruker 400 MHz instrument with the kind assistance of Mr. David D. 
Devore of the KSU Chemistry Department. 

Infrared spectra of the solid particles obtained after 
solvent evaporation were recorded on a Perkin-Elmer 1330 IR 
spectrophotometer with data station. 

Scans were accumulated either 20 or five times and added 
together and stored on the data station's memory. A correction 
program entitled FLAT was used to correct for the sloping baseline 
resulting from the pressed KBr pellets used. 

Electrophoresis measurements were obtained with a solution 
electrophoresis cell constructed by the author after a design by 
Burton (173). Electrophoretic mobilities were measured with a 
Seiko Chronograph Wristwatch against millimeter graph paper. 

The solid material obtained from the removal of the 
dispersion medium by vacuum distillation was pyrolyzed in the 
following way: The solid material was contained in a concentric 
trap constructed of stainless steel tubing and Swage-lok TM 
fittings. This trap comprised one loop attached to a four-way 
injection valve. The other loop connected to the chromatography 
column and ultimately the mass spectrometer (Finnegan Model 4000 
quadrupole GC-MS , ionization energy 35 eV, used in electron 
impact mode). The mass spectra of the pyrolysis products were 


recorded as the material eluted from the column. 

X-ray photoelectron spectra of the dry colloidal particles 
were collected by Dr. Peter M.A. Sherwood, Mr. Kevin Robinson and 
Mr. Guy Wilson of the KSU Chemistry Department on a VSW 100 C/ 
Apple instrument. 

Elemental analyses for metal, carbon and hydrogen were 
carried out by Galbraith Laboratories of Knoxville, TN. 

Electron paramagnetic resonance spectroscopy was carried out 
on the departmental Varian/IBM instrument by Dr. Ileana Nieves- 


IV. 2. Summary of Reactions 

Page# in 

Mass of Metal 

Volume of 



0.2609 g Au 

50 mL EtOH 



1.1810 g Au 

50 mL EtOH 



AgCl 0.7402 g 

25 mL EtOH 




Au 0.0912 g 


65 mL EtOH 



Au 0.0844 g 

100 mL EtOH 



Au 0.0271 g 

90 mL EtOH 



Au 0.8179 g 

100 mL EtOH 



0.0265 g Au 

140 mL Acetone 



Ag 0.4812 g 

120 mL Acetone 


Au 0.1946 g 

71 Cu 0.3075 g 

p. 73 Au 0.0562 g 
p. 80 Au 0.0222 g 

p. 81 Au 0.0024 g 

p. 82 Au 0.0886 g 
p. 83 Au 0.0114 g 

55 mL Acetone 






136 mL Acetone 






66 mL Acetone 






44 mL Acetone 





103 mL Acetone 






66 mL Acetone 

56 mL Acetone 

160 mL Acetone 
82 mL Acetone 

135 mL Acetone 

97 mL Acetone 
180 mL Acetone 


orange green matrix 
— > pptd black solid, 
red matrix, turned green, 
black sol, pttd 24 hours, 
yellow matrix — >orange 
sol lg. pink particles, 
orange/red matrix 
greenish matrix — >purple 
sol — >pptated. 
greenish matrix — >purple 
sol — >pptated - 2 hrs. 
purple sol — >pptated - 
2 hrs. 

bubbling observed in 

purple-brown sol- stable 

black sol, black matrix 
pptated (not protected 
from light). 

purple sol 

purple liq. 
purple liq (MTF-63-S-01) . 
purple liq (MTF-65-S-01 ) . 

purple liq (MTF-67-S-01 ) 
green-black matrix, black 
sol — >ppted, green powder 
green-black matrix, green 
sol — >pptated 

purple sol. 
bubbles on warmup, cold, 
empty dewar warmup 

v. dilute purple 
purple sol. 

spectral grade acetone 
stable 1 hr. 


Page# in Mass of Metal 
Notebook Evaporated 

p. 84 Au 0.0202 g 

Au 0.0286 g 

Au 0.0530 g 

Au 0.0116 g 
Au 0.0441 g 
Au 0.3673 g 

Au 0.0466 g 

Au 0.1095 g 

Au 0.0587 g 

Cu 0.1033 g 
Cu 0.0530 g 

Ag 0.3550 g 
Ag 0.0142 g 

Cu 0.0521 g 

Ag 0.1046 g 

Au 0.0105 g 
Ag 0.2010 g 

p. 114 Cu 0.0439 g 

p. 125 Ag 0.2502 g 

p. 126 Cu 

p. 127 Ag 0.1770 g 

p. 129 Ag 0.0130 g 

p. 130 Ag 0.0316 g 

























Volume of 

76 mL Acetone 

137 mL Acetone 
81 mL Acetone 

138 mL Acetone 
81 mL Acetone 
147 mL Acetone 

83 mL Acetone 

114 mL Acetone 

63 mL Acetone 

58 mL Acetone 
44 mL Acetone 

89 mL Acetone 
41 mL Acetone 

108 mL DMF 

74 mL DMF 

199 mL Acetone 
95 mL Acetone 

79 mL Acetone 
159 mL Acetone 

83 mL Acetone 

107 mL Acetone 
96 mL Acetone 
95 mL Acetone 


spectral grade acetone 
stable indefinitely 

pressure fluctuations 
— > pptated. 
ET0H slush warmup 

MeOH slush — >pptated. 
MeOH slush (MTF-88-S-01 ) , 

pentane slush 
pentane slush overnight 

EtOH slush overnight 
MeOH slush overnight 
black colloid — >pptated. 
black colloid when cold 
pptated on warmup. 
black colloid — >pptated. 
reddish matrix 
black colloid — >pptated. 
bubbled during warmup 
formed yellowish matrix, 
bubbled during warmup 
formed silver sponge. 

purple sol. 
airlessly handled but 
exposed to light. Color 
change from purple/black 
to gray. 

green sol handled 

greenish matrix, stored 
in dark — retains dark 
coloring when stored 
in dark. 

green sol-reacted W/H2O 
to release bubbles — > 
flame test revealed gas 
to be H2. 

black colloid, stored 

black colloid, stored 

black colloid, stored 


Au - Concentration Study : 

Au - Preliminary Study : 

Au - Warmup Studies : 

Au - Warmup Studies - Slushes : 

Ag - Concentration Study : 
MTF-113-S-01 (not exposed to light) 

Ar Colloid - Exposed to Light : 
(J00288 not exposed) 
(J00289 exposed 1 day) 



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176. J.T.G. Overbeeck, Kolloidchem. Beihefte , (1943), 54, 287. 

177. B.V. Deryagin & L. Landau, Acta. Physiochim. URSS , (1941), 

14, 633; E.J.W. Verwey & J.T.G. Overbeeck, "Theory of 
the Stability of Lyophobic Colloids,", Elsevier, 
Amsterdam, 1948. 

178. C.R.C. Handbook of Chemistry and Physics, 59th ed . , CRC 

Press, Boca Raton, Florida, 1979, pp. F-52 and E-55. 

179. Ibid. 

180. B. Jirgensons & M.E. Straumanis, "A Short Textbook of 

Colloid Chemistry", 2nd ed., MacMillan, New York, 
1962, 132. 

181. Ibid, p. 343. 


182. J.R. Vickery, Dept. Sci. Ind. Research Rept. Food 

Investigation Board 1929 , (1930), 24. 

183. C.J. Sandroff & D.R. Hershbach, Langmuir , (1985), 1(1) , 


184. D.J. Shaw, "Introduction to Colloid and Surface Chemistry", 

2nd Ed., Butterworths , London, 1970, 159. 






B.A., Central College, 1983 


submitted in partial fulfillment of the 
requirements for the degree 


Department of Chemistry 

Manhattan, Kansas 


Gold atoms, when co-condensed with acetone or other organic 
vapors in a cryogenic matrix at low pressure and subsequently 
warmed up slowly, will cluster in a controlled way to yield 
colloidal particles of gold suspended in the organic liquid, 
this method has been found to work also for silver, and less 
successfully with copper. 

The colloidal particles were found to form conductive metal 
films when the solvent is removed by evaporation. 

The colloids were characterized by electron microscopy, 
electrophoresis, UV-visible and NMR spectroscopy. 

The films were characterized by pyrolysis/gas chromatography- 
mass spectrometry, and infrared spectroscopy. 

It was concluded that the colloidal particles were stabilized 
by a combination of adsorbed solvent and by a buildup of negative 
charge on the particles.